Analysis on Stress State of Box-Girder Web under Prestressing

2014 ◽  
Vol 602-605 ◽  
pp. 33-36
Author(s):  
Bao Jun Zhao ◽  
Guo Rui Zhu ◽  
Liang Yin
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Cross Section ◽  
Element Model ◽  
Neutral Axis ◽  
Curved Beam ◽  
Box Girder ◽  
Principal Compressive Stress ◽  
Principal Tensile Stress ◽  
The Web

In order to study the stress of box-girder web under prestressing, and confirming the internal stress distribution of the web, analyzing of vertical prestressed box girder, curved beam prestressed sensitivity under the webs. Establishing finite element model of the box-girder webs vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L/4 section of the web.

scholarly journals Analysis on stress state of box-girder web under prestressing effect

2018 ◽  
Vol 17 ◽  
pp. 03007
Author(s):  
Haijun Yin ◽  
Ziqing Li ◽  
Xianwu Hao ◽  
Baojun Zhao
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Cross Section ◽  
Neutral Axis ◽  
Curved Beam ◽  
Stress Effect ◽  
Box Girder ◽  
Principal Tensile Stress ◽  
Bending Radius ◽  
The Web

In order to study the effect of prestressed box girder webs stresss state, determining the stress distribution within a web, research and analysis of vertical prestressed box girder, curved beam prestressed sensitivity under the web. Establishing the finite element model of the box girder web vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L / 4 section of the web. Calculation and analysis of curved beam under bending point, different bending angles and bending radius of principal stress effect on the web, Results show that the set of curved beam web when the curved beam bending stress concentration easily, appear the main tensile stress; Increase the bending radius can effectively reduce beam cross-section of web principal tensile stress, along with the rising of the next corner, principal tensile stress peak value increases gradually, thus setting bending beam, should try to reduce the bending angle.

Theoretical Analysis of Temperature and Shrinkage Stresses of Box-Girder Section

2011 ◽  
Vol 243-249 ◽  
pp. 1885-1892
Author(s):  
Wei Zhao Li ◽  
Zong Lin Wang ◽  
Fadhil Naser Ali
Keyword(s):  
Tensile Stress ◽  
Cross Section ◽  
Temperature Difference ◽  
Negative Temperature ◽  
Shrinkage Stress ◽  
Box Girder ◽  
Stress Changes ◽  
Longitudinal Cracks ◽  
Bottom Slab ◽  
The Web

The objective of this study is to analyze the temperature and shrinkage stresses of the mid-span cross-section of a 20 meters box girder to find the reasons which cause the longitudinal cracks in the web and bottom of box girder. According to the results of damage inspeation, there are many longitudinal cracks in the web and bottom slab of box girders, especially the web of the edger beam, the crack is very clear. Ansys ver.10 software is used to analyze two dimensional finite element model of a typical cross section of a real bridge to calculate the temperature stresses caused by temperature difference between inside and out side of the box and the shrinkage stresses based on moisture diffusion. The results of analysis show that the outer surface of the web and bottom slab of the fabricated box girder will produce tensile stress at the effect of negative temperature difference. If the concrete reaches a certain age, the tensile stress does not cause creaks in the cross-section. The shrinkage stress changes with the moisture gradient in the box section. It will reach the maximum in 15 days and then decreases with the growth of the age. Shrinkage stress may cause cracking of the concrete surface because of the tensile strength is low in the early age.

scholarly journals VII.—Rupture Stresses in Beams and Crane Hooks.

1914 ◽  
Vol 50 (1) ◽  
pp. 211-223
Author(s):  
Angus R. Fulton
Keyword(s):  
Compressive Stress ◽  
Cross Section ◽  
Bending Moment ◽  
Neutral Axis ◽  
Sectional Area ◽  
Inverse Proportion ◽  
Direct Loading ◽  
The Cross ◽  
External Forces ◽  
Distribution Of Stress

CONCLUSIONS1. It may be taken as conclusive that the final distribution of stress at rupture point in a member subjected to an external bending moment is a rectangular one, unless where the cohesion of adjacent layers is not sufficient to withstand the shear induced by the resisting moment of the section.2. That, provided shear does not take place, the neutral axis moves always to the position which reduces the summation of the tensile and compressive stress areas, across a section, to the equilibrant of the external forces. (In the case of a beam this reduces to zero; in that of a hook, at the principal section to the suspended weight.)3. That the total resisting moment of these stresses must be equal to the external bending moment as measured to the neutral axis at rupture point, but that these balancing moments do not differ materially from those measured to an axis obtained by dividing the sectional area into tensile and compressive stress areas which are in inverse proportion to the magnitude of their respective ultimate direct stresses.The advantage of these formulæ are important. It is possible to indicate with certainty the magnitude of the load which will cause rupture in a beam or a hook provided there is known the point of application or the effective arm of the load, the cross-section of the beam or hook, and the breaking strengths of the material when subjected to the different forms of direct loading.

Analysis of the Arrangement of Prestressed Steel in Web of Continuous Concrete Box-Girder Bridges

2014 ◽  
Vol 587-589 ◽  
pp. 1359-1363
Author(s):  
Lan Qiao ◽  
Shao Wen Zhang
Keyword(s):  
Tensile Stress ◽  
Large Scale ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Long Span Bridges ◽  
Girder Bridges ◽  
Principal Tensile Stress ◽  
Diagonal Section ◽  
Bridge Girder ◽  
Concrete Box Girder Bridges

Concrete continuous box- girder bridges have a large proportion in small span and long span bridges, and it has very broad prospects for development. Along with the large-scale construction of this kind of bridge, various problems have also emerged, especially the damage of RC beam’s diagonal section in bridge girder deflection. It always appears the inclined cracks in webs which cause by principal tensile stress, so it will be the potential damage to the whole bridge. However, the existence of the vertical prestress, will make the principal tensile stress of box girder in greatly reduced. So as to make cracking resistance performance of diagonal section is better than the ordinary reinforced concrete bridge. For an engineering example, this paper puts forward several different vertical prestressed steel arrangements. Based on different decorate a form of vertical pretressd bridge girder under stress numerical simulation, it is concluded that bridge’s web principal tensile stress distribution and its variation law, and then optimize the vertical reinforcing steel arrangement, improve the overall safety of bridge structure. It can provide the reference in the process of construction when we face the similar problems in the future.

Optimization Study on Open Shaped Ribs Arrangement and Diaphragm Cutout for Steel Orthotropic Box Girder

2012 ◽  
Vol 443-444 ◽  
pp. 1072-1077
Author(s):  
Zhen Wang Wu ◽  
Kai Feng Zheng ◽  
Ying Jie Cui ◽  
Yan Bin Shui
Keyword(s):  
Finite Element ◽  
Parameter Optimization ◽  
Element Model ◽  
Vertical Load ◽  
Box Girder ◽  
Tangential Stresses ◽  
Vehicle Load ◽  
Optimization Study ◽  
Transverse Position ◽  
The Web

The ramp B of one overpass was designed as curved steel orthotropic box girder, whose deck was welded with open shaped bulb ribs in the range of driveways. Then, one detailed finite element model was built to simulate the structure. For the two arrangements of bulb towards and back to web in the cantilever, the tangential stresses of diaphragm cutout were compared under the action of vehicle load. In accordance with above research, it can be concluded that the stress will be more reasonable with the bulb back to web. After altering the transverse position of the vehicle load and calculating the tangential stress along the edge of diaphragm cutout, based on further analysis, it’s generally believed that the following two reasons made the arrangement of bulb back to web more appropriate at least. First of all, the diaphragm connected with the rib adjacent to the web could share part of vertical load. What's more, it could increase the distance from the edge of the cutout to the web center. What come next was to change the diaphragm cutout size, and that parameter optimization was carried out. The results show that a radius of 40-50mm is more applicable for the arc on the bottom of the diaphragm cutout.

scholarly journals Finite Element Analysis and Optimization of Steel Girders with External Prestressing

2018 ◽  
Vol 4 (7) ◽  
pp. 1490 ◽  
Author(s):  
Ali Laftah Abbas ◽  
Abbas Haraj Mohammed ◽  
Raad Dheyab Khalaf ◽  
Khattab Saleem Abdul-Razzaq
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Element Model ◽  
Bottom Flange ◽  
Element Analysis ◽  
Steel Girder ◽  
Finite Element Software ◽  
External Prestressing ◽  
Design Variables ◽  
The Web

Optimization is a process through which the best possible values of design variables are achieved under the given of constraints and in accordance to a selected optimization objective function. Steel I-girders have been used widely in different fields, which are generally fabricated by connecting two plate flanges, a flat web and a series of longitudinal or transverse stiffeners together. The use of steel girder with external prestressing has been used in many countries as a means of strengthening bridges. The purpose of this paper is to develop a finite element model for the optimization of a steel girder with external prestressing. The ANSYS finite element software package was used to find the optimum cross section dimension for the steel girder. Two objective functions are considered in this study there are optimization of the strain energy and total volume of the girder. The design variables are the width of top flange, the thickness of top flange, the width of bottom flange, the thickness of bottom flange, the height of the web, the width of the web and area of prestressing tendons. Two type of steel girder are considered there are steel girder without prestressing and steel girder with prestressing. The results for volume minimization shows that the optimum cross section for steel girder with prestressing smaller than for steel girder without prestressing.

Stress Analysis of a Novel MEMS Microphone Chip Using Finite Element Analysis

2005 ◽  
Author(s):  
Jia Gao ◽  
Ronald N. Miles ◽  
Weili Cui
Keyword(s):  
Finite Element ◽  
Low Temperature ◽  
Tensile Stress ◽  
Finite Element Model ◽  
Oxide Layer ◽  
Compressive Stress ◽  
Failure Modes ◽  
Element Model ◽  
Mems Devices ◽  
Mems Microphone

Residual stress produces major challenges in the fabrication of MEMS devices. This is particularly true in the development of MEMS microphones since the response of the thin sound-sensitive diaphragm is strongly affected by stress. It is important to predict the effects of fabrication stress on the microphone chip and identify the failure modes to ensure a satisfactory fabrication yield. In this study, a finite element model of the microphone chip is developed to analyze the laminated structure under different fabrication stresses. The model of the microphone chip includes the diaphragm, backplate and sacrificial oxide layers on top of the silicon substrate. Fabrication stresses are included through the use of an equivalent thermal stress. The stresses in the different layers have been estimated based on measurements performed on fabricated test structures. The estimated stresses are simulated in the finite element model. An important factor in determining the process reliability is the compressive stress of the low temperature sacrificial oxide layer (LTO). A variety of stress combinations between different layers with the low temperature oxide layer are investigated. It is found that an adequate level of tensile stress in the backplate is crucial to ensure the fabrication yield. In the designs considered here, silicon nitride in combination with a thin conductive layer is identified as a favorable material for the backplate considering its high modulus and tensile stress in ‘as deposited’ film. In addition, the presence of a LTO layer on the backside of the wafer turns out to be very helpful in reducing the deflection of the unreleased chip and the stress in the diaphragm. In the case where there is a net compressive stress in the laminate, the failure mode is identified by nonlinear analysis. This analysis provides a guideline to select robust materials and tune the fabrication process to ensure a satisfactory fabrication yield.

Long-Term Performance of Concrete Suffered Infant Age Freezing

2012 ◽  
Vol 174-177 ◽  
pp. 524-529 ◽  
Author(s):  
Bao Lin Guo ◽  
Chang He Yu ◽  
Yu Han ◽  
Ju Peng Zhu
Keyword(s):  
Calcium Carbonate ◽  
Cross Section ◽  
Box Girder ◽  
Cover Concrete ◽  
Concrete Quality ◽  
Complicated Process ◽  
Long Term Performance ◽  
Term Performance ◽  
The Web

Interior water migrated towards the surface area when concrete suffered minus temperature during infant ages. Cover concrete became the worst part after the complicated process of water freezing – thawing, intermittent hydration of cementious materials and volatilization. Presentation quality, carbonization depth and rebound value in 120 d ages were observed and tested in situation. There were some calcium carbonate stains spread over the web, many swelling points and radial ice lens spread over the surface of box girder. The carbonization depth was over 10mm, and the rebound value of web concrete lower than 50, some areas’ lower than 35, variance larger than 30. Compared with other parts, the rebound value of web bottom concrete was the lowest and the variance biggest. For the same cross section, there were obviously difference of concrete quality between sunny face and shady ones, which enhanced the un-uniformity of element and made the stress distribution more complicated and uncertainty. Some effective measures must be taken to avoid the infant age frozen in order to assure the concrete quality constructed during the winter.

scholarly journals Analysis of the Static Behavior of a Single Tree on a Finite Element Model

Plants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1284
Author(s):  
Ľuboš Moravčík ◽  
Radko Vincúr ◽  
Zdenka Rózová
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Analysis ◽  
Tensile Stress ◽  
Finite Element Model ◽  
Cross Section ◽  
Element Model ◽  
Tree Structure ◽  
Element Analysis ◽  
Whole Tree

This work deals with the innovated complex process of tree risk assessment, from precise geometrical tree shape acquisition to building and analyzing a finite element model under specified load. The acquisition of the 3D geometry of the tree was performed by means of terrestrial laser scanning. Obtained point cloud was optimized and additionally converted to a 3D CAD model, representing the bearing skeleton compound of trunk and main branches. For structural analysis purposes, a finite element model (FEM) was built in the form of beam structure fixed to the ground. Particular beams were defined by geometry, material properties of wood, and cross sections. An acoustic tomography was applied for determination of the precise cross section on investigated locations of an analysis model. Finite element analysis performed on the computational model shows the bearing capacity and deformations of the whole tree structure caused by combinations of load cases like self-weight and static equivalent of wind load. The results of the structural analysis called attention to potentially dangerous places within the tree structure with extreme node displacements or tensile stresses on beams. Thus, we observed a maximal horizontal displacement of 280.4 mm in node N34 and dangerous tensile stress in node N26, where it reaches +23.6 MPa. After filtering some beams with an abnormal cross section geometry, the finite element analysis of the whole tree structure showed the highest tensile stress of +8.8 MPa and highest compressive stress of −8.9 MPa. The suggested method can be applied generally for the prediction of potentially risky tree suspected of breakage and especially for monumental trees, where the presented method can be mostly applicable.

Monolithic Roadbed's Mechanical Behavior Affected by Structural Thickness under Tram

2013 ◽  
Vol 361-363 ◽  
pp. 1664-1670
Author(s):  
Chong Wei Huang ◽  
Er Hao Su ◽  
Xian Zhi Shao ◽  
Yi Zhang ◽  
Lie Ping Wang
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Tensile Stress ◽  
Mechanical Behavior ◽  
Compressive Stress ◽  
Contact Problems ◽  
Element Model ◽  
Nonlinear Contact ◽  
Structure Layer ◽  
Abaqus Software

Based on ABAQUS software, a 3-D finite element model which content the nonlinear contact problems and contact-earth subgrade-monilithic was given to analysis the mechanical behavior of the monolithic roadbed. Mechanics behavior and deflection of the monolithic roadbed, deflection and compressive stress of earth subgrade evaluated in detail with respect to varied structure layer combination and materials parameters. The results indicate that the increase roadbed thickness can significantly reduce the monolithic roadbeds tensile stress, which can reach 1.042MPa. With the increase of the friction coefficient, level of tensile stress σdy, monolithic deflection Dd , the compressive stress σsz and deflection on earth subgrade were slightly reduced.

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